The present invention relates generally to a circuit breaker. More specifically the present invention relates to an arc fault circuit breaker.
Arc fault circuit breakers are well known. These breakers comprise contacts that open upon sensing arcing from line to ground, and/or from line to neutral. Arc fault circuit breakers typically use a differential transformer to measure arcing from line to ground. Detecting arcing from line to neutral is accomplished by detecting rapid changes in load current by measuring voltage drop across a relatively constant resistance, usually a bi-metal resistor.
Components of arc fault circuit breakers are generally assembled into separate compartments as defined by their function. More specifically, mechanical components, e.g., load current carrying and switching components, of each pole are assembled into mechanical compartments, while the current sensing components are assembled into an electronics compartment. In order to connect the compartments, the load current of each pole must be routed from the mechanical compartments into the electronics compartment, through appropriate current sensing devices, and back into the mechanical compartments. Additionally sensing lines, e.g., from the bi-metal resistors, must also be routed from the mechanical compartments into the electronics compartment. Because these circuit breakers sense arc faults, which are essentially short circuits, the connections of the load current carrying components throughout the circuit breaker must be capable of withstanding enormously high surge currents, sometimes in excess of 10,000 amps. The stresses caused by these extremely large surge currents can blow a connection apart that is not manufactured to proper quality standards. This means that during the assemble process, high quality connections, e.g., welds, bolts, or crimps, must be carefully made and inspected in order to survive the extremely high surge currents, and must be completed at a rate that meets the production schedule.
The electronics compartment typically includes a solenoid having a plunger shaft with a right-angle plunger arm attached at one end thereof. During assembly of the circuit breaker, the plunger arm must drop into a slot in the mechanical compartment for activating a trip mechanism during operation. It will be appreciated that since the plunger shaft is cylindrical, both the plunger shaft and the plunger arm attached to it easily rotate. When the electronics compartment is mated with the mechanical compartment, the plunger arm has been known to rotate in such a manner that it wedges between the two compartments.